From DE 195 15 338 A1 a rotation speed sensor is known, which comprises a magnet and, cooperating with it, two Hall elements arranged a lateral distance apart, past which a component made of a ferromagnetic material and having an irregular circumference or a circumference with discontinuities can be moved in the direction of the lateral separation. With the aid of this rotation speed sensor, a speed of the component during it rotation or, if the component is at rest, a particular position of the component relative to the speed sensor can be determined. This information can be converted into a corresponding signal, which can be processed further by appropriate electronic equipment.
Such speed sensors, which are also used in industry, measure magnetic flux density changes produced by a rotating component or so-termed “signal wheel”. From these flux density changes, the two Hall elements each produce a continuous sensor signal, whose wave-shaped variation depends on the distance between the speed sensor or a sensor device comprising the Hall elements, and the said signal wheel.
If the sensor signals exceed predetermined switching thresholds, respective alternating switching signals are sent to the sensor device which, in turn, emits a pulse signal to an evaluation unit which is evaluated in order to calculate a speed of the component or signal wheel electronically.
Owing to production-related running of the signal wheel out of true so that it deviates from an ideal condition, and owing to distance differences during a rotation of the signal wheel and while it is at rest, arrangements with a sensor device and a signal wheel are characterized by large dynamic and static air-gap ranges and, therefore, require sensors with a wide measurement range which can determine an operating condition of the signal wheel with high sensitivity, i.e., even with sensor signals of small amplitude and at the same time low switching thresholds of the sensor device.
The desired high sensitivity of sensor devices, however, especially when there are vibrations of the signal wheel caused for example at rest by rotation oscillations of the signal wheel, leads disadvantageously to the calculation of a rotation speed of the signal wheel, since pulse signals are emitted by the sensor device even though the signal wheel is not physically rotating. To increase insensitivity to vibrations, sensor devices with lower sensitivity are used, i.e., ones with higher switching thresholds, but these have the disadvantage of a smaller working range.
Thus, the above-mentioned requirements for the largest possible working or measurement range of the sensor devices, at the same time with high sensitivity for the determination of an operating condition of a signal wheel, represent conflicting demands since the insensitivity of a sensor device to vibrations is less good if its working range is larger, or the working range of a sensor device is smaller if at the same time, its insensitivity to vibrations is improved.
Accordingly, the purpose of the present invention is to provide a method for determining the rotation speed and rotation direction of a component with a sensor device with which the rotation speed and direction of the component can be determined over large working ranges even in the presence of substantial vibrations.